Electrical terminal or tap for a strip wound coil and method of making the same



April 18, 1967 .E. KOCH ETAL 3,315,199

AND

ELECTRICAL TERMI OR TAP FOR A STRIP WOUND COIL METHOD OF MAKING TH AME Filed Aug. 13, 1

EM/ 7M,

United States Patent Ofifice 3,315,199 Patented Apr. 18, 1967 3,315,199 ELECTRICAL TERMINAL R TAP FOR A STRIP gVOUND COIL AND METHOD OF MAKING THE AME Robert E. Koch, Pittsfield, and Willard F. M. Gray,

Hancock, Mass., assignors to General Electric Company, a corporation of New York Filed Aug. 13, 1965, Ser. No. 479,560 8 Claims. (Cl. 336-192) This invention relates to electrical terminals or taps for conductive strip wound coils and to a method of making the same.

Strip wound coils have a number of advantages over wire wound coils. One important advantage is that they have a higher space factor, i.e., a higher roportion of the over-all coil volume is occupied by the conductor material. However, they have a disadvantage in that it is more diflicult to attach terminals or taps to them without substantially decreasing their space factor.

In accordance with the present invention, this problem is overcome by flush butting a conductive tab of the same thickness as that of the strip against a side edge of the strip, backing both the tab and strip (adjacent the tab for its full width) with a thinner sheet of conductive material and bonding all three parts together preferably by carbon block brazing.

An object of the invention is to provide a new and improved tab terminal or tap for a strip wound electrical coil or solenoid.

Another object of the invention is to provide a new and improved method of making such a tab connector.

A further object of the invention is to provide a new and improved strip wound electrical 'coil or solenoid and method of making the same.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing,

FIG. 1 is a perspective view of a strip wound coil embodying the invention,

FIG. 2 is a sectional view of the outer tab terminal construction taken on line 2-2 of FIG. 1,

FIG. 3 is a broken away perspective view of the principal parts of the outer layer of the coil,

FIG. 4 is a view similar to FIG. 3 for the inner layer of the coil,

FIG. 5 is a view showing the step of carbon block brazing the outer tab terminal assembly.

Referring now to the drawing and more particularly to FIG. 1, there is shown therein an electrical coil winding or solenoid 1 comprising interleaved and spirally wound strip conductor 2 and layer insulation 3. The conductive strip 2 may be made of any suitable material such as copper having a thickness range of 60 mils to 15 mils, for example. The interleaved strip of insulating material 3 may be made of any suitable material such as high temperature resistant paper or other suitable Class H insulation. Preferably, it is appreciably wider than the conductive strip 2 so that its side edges extend beyond the side edges of the conductive strip 2 to provide additional insulation at the ends of the coil layers or turns which in the case of a strip wound coil having concentric turns as shown are the same in number. The outer layer or turn of the conductive strip is shown in phantom as terminating at 4, but the strip of insulating material 3 is carried on and wrapped one or more times around the coil to provide outer insulation, this outer wrapping being held in place by any suitable material such as an adhesive binding tape 5.

For attaching leads such as flexible cables 6 to the ends of the coil, there is provided a construction which is shown in more detail in the remaining figures.

Referring now to FIG. 2, which omits the layer insulation 3 in order to simplify the showing, the connection to the outer and upper end of the coil as shown in FIG. 1 is made by means of a tab 7 of conductive material preferably the same as that of the conductive strip 2 and of the same thickness which is brazed in flush butt contact with the edge of the conductive strip 2 adjacent its end. Parts 2 and 7 are backed by a relatively thin sheet 8 of conductive material also preferably of the same composition as that of the conductive strip 2 and the tab 7. A suitable thickness for the backing sheet 8 is 10 mils. These parts are then all conductively bonded together preferably by carbon block brazing as will be described in more detail hereafter. This has the advantage over torch brazing or butt welding in that it is not necessary to attain as high temperatures as with the latter because heat is applied uniformly over the whole surface of the backing sheet 8 and the opposite sides of the conductive strip 2 and tab 7 so that heat is not conducted so rapidly away from the flush butt joint between the strip 2 and the tab 7.

The cable 6 may have its end solidified as at 9 and parts 9 and 7 can then be conductively bonded together in any suitable manner such as by brazing.

FIG. 3 shows that the backing sheet 8 is as wide as the tab 7 and as long as the combined length of the tab 7 and the width of the strip 2, i.e., the backing sheet 8 extends the full width of the strip 2 and the full length of the tab 7. FIG. 3 also shows that the tab 7 is substantially narrower than the conductive strip 2 and is about as long as it is wide. While the tab 7 has substantially less current carrying cross sectional area than that of the conductive strip 2, it has been found that its temperature rise in operation does not exceed that of the strip 2. This is believed to be due to the extra current carrying area of the backing sheet 8, the comparative shortness of the tab 7 and its exposure to the ambient medium.

The tab construction at the opposite or inner end of the coil is generally the same as for the outer end of the coil and is shown in more detail in FIG. 4 in which a tab 7 corresponding to tab 7 is flush butted against the opposite edge of the conductive strip 2 at its lower or inner end, the tab 7 and the strip 2 being backed by a sheet 8 corresponding to sheet 8, these parts being bonded together as for the outer tab construction. In practice, it is simpler to form the inner or start tab construction first when the parts are flat and then start winding the coil on a suitable mandrel and after the required number of turns have been wound, the outer or outer end terminal construction is formed in the same manner as for the inner end at which time the strips of conductive material 2 and insulation 3 are cut so that a new coil can be started from the cut end.

The thinness of the backing sheets 8 and 8 does not produce any appreciable eccentricity in the coil. It will be observed, however, that the inner or lower and outer or upper tab constructions are angularly displaced ninety degrees so that whatever eccentricity each backing sheet does produce will not be cumulative as it would be if the two terminal constructions were on a common diameter of the coil.

FIG. 5 shows the outer end of the conductive strip 2, the tab 7 and the backing sheet 8 all clamped between carbon blocks 1d which are substantially coextensive with the outer surfaces of the parts to be bonded. Preferably, a thin strip of silver alloy (not shown) is inserted between the bac ing sheet on the one hand and the conductive strip 2 and the tab 7 on the other hand. When a sufficiently high electric current is caused to flow between the carbon blocks, the conductive parts therebctween are heated by the FR effect of the current in the blocks and parts to be bonded and when the temperature reaches the melting point of the silver alloy, it flows and alloys with the copper forming an alloy having a lower melting point than that of the copper so that the parts are intimately and strongly joined at a temperature below the melting point of copper. The curent is then turned off and the carbon blocks removed.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention, and therefore it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What We claimas new and desire to secure by Letters Patent of the United States is:

1. A method of forming an electrical terminal or tap on a coil forming strip of conductive material comprising the steps of flush butting an end of a conductive tab of the same thickness as said strip against a side edge of said strip, laying a conductive backing sheet which is substantially thinner than said strip across said strip and tab in bridging relation thereto, and conductively bonding and strip, tab and sheet together.

2. The method as in claim 1 in which the bonding step comprises carbon block brazing.

3. In combination, a conductive strip many times wider than it is thick and many times longer than its width for flatwise winding to form an electrical coil, a conductive tab of the same thickness as but substantially less wide than said strip having one end in flush butt contact with a side of said strip, and a conductive backing sheet substantially thinner than the thickness of said strip of a width equal to the width of said tab and of a length equal to the sum of the width of said strip and the length of said tab laid fiatwise congruently in bridging relation across said tab and strip, the contacting surfaces of said strip, tab and sheet being conductively bonded to each other.

4. In combination, a conductive strip many times wider than its thickness and many times longer than its width for flatwise winding to form an electrical coil whose axial extent corresponds to the Width of said strip, a conductive tab of the same thickness as but substantially less wide than said strip having one end in butt contact with a side of said strip adjacent one end thereof, and a conductive backing sheet substantially thinner than the thickness of said strip of a width equal to the width of said tab and of a length equal to the sum of the width of said strip and the length of said tab laid flatwise congruently in bridging relation across said tab and strip, the contacting surfaces of said strip, tab and sheet being conductively bonded to each other.

5. An electrical winding comprising an elongated conductor strip flatwise curved to provide a multi-turn coil, a conductive tab of the same thickness as that of said strip having an end flush butted in conductive contact with a side edge of said strip, a relatively thin backing sheet of conductive material in bridging conductive rela- 4 tion to said strip and tab on one side thereof over the Width of said strip and the length of said tab, said strip, tab and sheet being conductively bonded to each other.

6. An electrical winding comprising an elongated conductor strip flatwise curved to provide a multiturn coil with ends on radii angularly displaced ninety degrees from each other, a conductive terminal tab of the same thickness as that of said strip having an end flush butted in conductive contact with an edge of said strip at one end, a relatively thin backing sheet of conductive material in bridging conductive relation to said strip and tab on one side thereof over the width of said strip and the length of said tab, said strip, tab and sheet being conductively bonded to each other, a second conductive terminal tab of the same thickness as that of said strip having an end flush butted in conductive contact with the other edge of said strip at its other end, a second relatively thin backing sheet of conductive material in bridging relation to said strip and last mentioned tab on one side thereof over the width of said strip and the length of said tab, said last mentioned tab, said strip and said last mentioned sheet being conductively bonded to each other.

1-. A solenoid comprising an elongated conductor strip flatwise curved in a tight spiral of concentric insulated turns in series between a radially inner end and a radially outer end to provide a multi-layer, multi'turn coil having the same number of layers as turns with the radially outer end having a substantially greater radius of curvature than the radailly inner end and with said ends on radii angularly displaced ninety degrees from each other, a radially outer conductive terminal tab of the same radius of curvature as the radially outer end of said strip of the same thickness as that of said strip having an end flush butted in conductive contact with an edge of said strip at its radially outer end, a relatively thin backing sheet of conductive material in bridging conductive relation to said strip and tab on one side thereof over the width of said strip and the length of said tab, said strip, tab and sheet being conductively bonded to each other, a radially inner conductive terminal tab of the same radius of curvature as the radially inner end of said strip of the same thickness as that of said strip having an end flush butted in conductive contact with the other edge of said strip at its radially inner end, a relatively thin backing sheet of conductive material in bridging relation to said strip and last mentioned tab on one side thereof over the width of said strip and the length of said tab, said last mentioned tab, said strip and said last mentioned sheet being conductively bonded to each other.

8. A solenoid as in claim '7 in which the width of said tabs is substantially less than the Width of said strip.

References Cited by the Examiner UNITED STATES PATENTS 217,466 7/1879 LeCowte 336--l92 X 2,599,508 6/1952 Allison 317260 X 3,153,216 10/ 1964 Klitten.

LEWIS H. MYERS, Primary Examiner.

E. GOLDBERG, Assistant Examiner. 

3. IN COMBINATION, A CONDUCTIVE STRIP MANY TIMES WIDER THAN IT IS THICK AND MANY TIMES LONGER THAN ITS WIDTH FOR FLATWISE WINDING TO FORM AN ELECTRICAL COIL, A CONDUCTIVE TAB OF THE SAME THICKNESS AS BUT SUBSTANTIALLY LESS WIDE THAN SAID STRIP HAVING ONE END IN FLUSH BUTT CONTACT WITH A SIDE OF SAID STRIP, AND A CONDUCTIVE BACKING SHEET SUBSTANTIALLY THINNER THAN THE THICKNESS OF SAID STRIP OF A WIDTH EQUAL TO THE WIDTH OF SAID TAB AND OF A LENGTH EQUAL TO THE SUM OF THE WIDTH OF SAID STRIP AND THE LENGTH OF SAID TAB LAID FLATWISE CONGRUENTLY IN BRIDGING RELATION ACROSS SAID TAB AND STRIP, THE CONTACTING SURFACES OF SAID STRIP, TAB AND SHEET BEING CONDUCTIVELY BONDED TO EACH OTHER. 